Spark plug

ABSTRACT

A spark plug for a combustion engine or a combustion chamber, in which the electrodes of ferrous metals or ferroalloys have a coating fused directly thereon by a process known in the art as &#39;&#39;&#39;&#39;electronic sputtering.&#39;&#39;&#39;&#39; The coating forms a very thin laminar deposit of a high temperature resistant metal, for example, one of the carbides of tungsten, titanium and chromium.

United States Patent Brennen 51 June 27, 1972 SPARK PLUG [72] Inventor:Ronald F. Brennen, 3921 Crystal Lake Drive, Pompano Beach, Fla. 33064[22] Filed: Sept. 21, 1970 [21] Appl. No.: 73,735

[52] US. CL. ..313/14l, 313/141.1

[51] Int. Cl ..H0lt 13/20 [58] FieldofSearch ..313/14l,l4l.1,31l

[56] References Cited UNITED STATES PATENTS 2,296,033 9/1942 Heller..313/l4lX Hensel ..3l3/14l.1 X Reijnhout "313/1411 PrimaryExaminer-Nathan Kaufman Att0rney-Ha.rry N. Schofer ABSIRACT A spark plugfor a combustion engine or a combustion chamber, in which the electrodesof ferrous metals or ferroalloys have a coating fused directly thereonby a process known in the an as electronic sputtering." The coatingforms a very thin laminar deposit of a high temperature resistant metal,for example, one of the carbides of tungsten, titanium and chromium.

5 Claims, 2 Drawing Figures P'ATENIEnJun'! m2 .IKVENTOR PONALD F.BPENNEN 1. Field of the Invention This invention relates to sparkproducing electrodes, and more particularly to the electrodes of ferrousmetals or ferroalloys for spark plugs operating in high temperatureenvironments such as, for example, the engine cylinders of internalcombustion engines, or for the purpose of igniting combustion chambers.

Spark plugs and the electrodes thereof operating in combustion chambersor engine cylinders where they are subjected to high temperatures areusually made ofhigh temperature steel. Because of the repeated arcingacross the electrodes at the existing operating temperatures, severepitting of the ends of the electrodes soon takes place, requiringfrequent replacement of the spark plugs. In an'automobile engine, forinstance, it is recommended that the spark plugs be replaced every8,000-l0,000 miles, while in airplane engines, where the failure of aspark plug may have more serious consequences, the recommendedreplacement period is much shorter.

2. Description of the Prior Art Various attempts have been made toprovide coatings of heat resistant metals on the electrodes of sparkplugs, but have not been successful as they call for brazing to bond thecoating to the metal of the electrodes. Under the high temperatureconditions in which the electrodes operate, the bonding material quicklyfails, and the coating is lost.

It is an object of this invention to provide a spark plug having a muchlonger useful life, requiring much less frequent replacement.

It is a further object to provide a novel spark plug in which theelectrodes are directly coated by fusing, without the interposition of abonding agent, with the high temperature resistant metal.

It is a still further object to provide a novel spark plug, theelectrodes of which are made of ferrous metals or ferroalloys, saidelectrodes having directly fused thereon,without the interposition of abonding agent,-by a process known in the art as electronic sputtering",a molecularly bonded coating of a carbide of one of the metals selectedfrom the group consisting of tungsten, titanium and chromium having athickness not exceeding 0.002inch.

SUMMARY OF THE INVENTION The attainment of the above objects, as well asother objects and advantages, is accomplished by depositing and fusing acoating not exceeding 0.002 inch of a high temperature resistantmaterial such as, for example, one of the carbides of tungsten, titaniumand chromium, directly to the metal of the electrodes, without theinterposition of an intermediate bonding agent. The high temperatureresistant material is deposited on the surface of the electrodes by aprocess known in the art as electronic sputtering. A device forproducing such a coating or deposit is disclosed in my copendingapplication, Ser. No. 73,736, filed on Sept. 21, 1970, entitled AnodicDepositor, now abandoned.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of theinvention, reference is made to the following specification describing apreferred embodiment in detail, and to the annexed drawing, in which:

FIG. 1 is an elevation view, partly in section, of a spark plug showinga coating on the electrodes thereof; and

FIG. 2 is an enlarged view, partly in elevation and partly in section,of the lower end of the spark plug of FIG. 1 showing my invention moreclearly.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the annexeddrawing, the numeral I0 designates a spark plug in its entirety, andincludes a shank 12 having a threaded portion 14 by which the spark plugmay be screwed into a cylinder head by means of a tool cooperating witha hexagonal nut 16. The upper end of the spark plug 10 includes a cap 18for attachment with a conductor receiving current from a source of highvoltage electricity to intermittently create a spark across the gap ofthe electrodes. The cap 18 is positioned at the upper end of a firstelectrode 22 which is insulated from the shank 12 by a porcelaininsulation 20, the electrode 22 passing through the entire length of thespark plug 10. The lower end of the spark plug is extended to form askirt 30 carrying a second electrode 24. The skirt 30 and threadedportion 14 provide a conductor with the engine block of the engine (notshown) to ground the electrode 24. The electrodes 22 and 24 are made offerrous metals or fer roalloys.

On the lower end of the electrode 22, and on the upper surface of theelectrode 24 in the area facing the electrode 22, there is deposited avery thin coating 26 of a high temperature resistant material such as,one of the carbides of tungsten, titanium and chromium. The surfaces ofthe coatings 26 are spaced to form a gap 28 across which a spark iscreated when a high voltage electrical charge is impressed across theelectrodes 22 and 24.

Spark plugs now in use, in which the electrodes are made of hightemperature steel, have a relatively short useful life. Because of thehigh temperature operating conditions under which they operate, and thehigh voltage arcs across the electrodes, the electrodes soon becomebadly pitted and are rendered useless. The addition of the coatings 26of a material that has a high wear resistance under the conditionsexisting in an engine cylinder or in a combustion chamber will greatlyextend the useful life of the spark plugs.

The coatings 26 are deposited directly on the metal of the electrodeswithout the interposition of any intermediate bonding agent such asbrazing and the like. In the practice of my invention, the metal coatingis electronically fused into the pores of the electrodes, and will notchip or peel.

The coatings 26 are deposited by a device known in the trade as asputterer" or metal depositor by a process known as electronicsputtering. An example of the device which may be used is disclosed inmy copending application, Ser. No. 73,736, filed on Sept. 21, 1970, nowabandoned. In this device, an electrode is vibrated rapidly to and froma work piece to be coated, about 60 times per second, or 3,600 times aminute. The work piece should be an electric conductive material, andthe vibrating electrode has a tip made of the metal to be deposited onthe surface of the work piece. The work piece and the vibrating tip areelectrically connected in a circuit which supplies an electric currentto the work piece and vibrating tip synchronously with the vibrations,so that each-time the vibrating tip contacts the work piece, a tinyparticle of the metal of which the tip is made is deposited andelectronically fused into the surface of the work piece. For every0.0.001 inch deposited below the surface of the work piece, an equalamount is deposited above the surface. The tip is moved relative to thesurface of the work piece over the required area as many times asnecessary to completely cover the area. The maximum thickness that acarbide of a metal can be deposited by this process is 0.002 inch.

As used in the subjoined claims, the term directly fused" refers to thefusion of a coating directly to the electrodes of the spark plug withoutthe interposition of any bonding agent, either as a separate material oras a material in the alloy of an electrode.

I claim:

1. A spark plug for a combustion engine or combustion chamber having apair of spaced electrodes exposed to high operating temperatures, saidelectrodes having thereon a coatcoating is not in excess of 0.002 inch.

4. A spark plug for a combustion engine or combustion chamber as definedin claim 1, in which the coating is deposited by an electronicsputtering process.

5. A spark plug for a combustion engine or a combustion chamber asdefined in claim 1, in which the electrodes are selected from the groupconsisting of a ferrous metal and a ferroalloy.

1. A spark plug for a combustion engine or combustion chamber having apair of spaced electrodes exposed to high operating temperatures, saidelectrodes having thereon a coating of a high temperature resistantmaterial selected from the group consisting of the carbides of tungsten,titanium and chromium.
 2. A spark plug for a combustion engine orcombustion chamber as defined in claim 1, in which the high temperatureresistant material is deposited as a very thin coating only on theportions of the electrodes facing each other.
 3. A spark plug for acombustion engine or combustion chamber as defined in claim 4, in whichthe thickness of the coating is not in excess of 0.002 inch.
 4. A sparkplug for a combustion engine or combustion chamber as defined in claim1, in which the coating is deposited by an ''''electronic sputtering''''process.
 5. A spark plug for a combustion engine or a combustion chamberas defined in claim 1, in which the electrodes are selected from thegroup consisting of a ferrous metal and a ferroalloy.